title: Azo doped polymer thin films for active and passive optical power limiting applications.
abstract: Two novel optical power limiters, 2-[ethyl-(4-phenylazo-phenyl)-amino]-ethanol (E4PA) and 2-[ethyl-(4-trifluoromethyl-phenylazo-phenyl)-amino]-ethanol (E4TPA) were synthesized using a diazotization reaction. The purified azo material was made into thin films in a poly(methyl methacrylate) matrix using a gravity settling technique. The electronic nonlinearities of these films were investigated using an open aperture Z-scan technique in the fs excitation regime, resulting in nonlinear absorption due to a two-photon absorption (2PA) process. The 2PA coefficient for these films is of the order 10(-12) m W(-1) and the limiting threshold values are 1.1 J cm(-2) each. A non-degenerate pump probe set-up was employed with CW lasers to study the nonlinear behaviour arising from photo-induced anisotropy and excited-state absorption. The present study shows that these azo thin films are potential candidates for active and passive optical power limiting applications.
authors.affiliation: Department of Physics, Sri Sathya Sai Institute of Higher Learning, Prashanti Nilayam, Andhra Pradesh 515134, India. sivasankarasai@sssihl.edu.in.
authors.forename: B
authors.initials: B
authors.lastname: Rajashekar
authors.forename: Sagar
authors.initials: S
authors.lastname: Limbu
authors.forename: Kamarusu
authors.initials: K
authors.lastname: Aditya
authors.forename: G
authors.initials: G
authors.lastname: Nageswara Rao
authors.forename: S
authors.initials: S
authors.lastname: Siva Sankara Sai